Door locks and Alarm help

My door locka nd alarm are all screwed up. I shut the driver side door and the locks start locking and unlocking for about 30 seconds and usually end up locked ( which is bad if you want to warm your car up ) I also have problems with the alarm, when I unlock and open the door the alarm goes off until I lock it and unlock it again.

I am thinking of getting an after market alarm. Would that solve both problems? What is a good alarm to go with and how much should it cost me to have it installed?